Heat 12-inch skillet over high heat until hot, 3 to 4 minutes. Add shrimp and cook, stirring every 10 seconds, until just opaque, about 1 minute. Push shrimp to sides of skillet, clearing a spot in the center of the pan. Add remaining 1 Tbsp. oil and scallion mixture to clearing and mash with spoon; cook until fragrant, 10 to 15 seconds, then stir mixture into shrimp. Remix tomato juice mixture and stir into skillet; cook until sauce has thickened, 30 to 45 seconds. Transfer to serving plate, sprinkle with reserved scallion greens, and serve.